1. Technical Field
The present invention generally relates to a method and system for managing communications networks. In particular, the present invention relates to a method and system for discovering topology in a SIP network.
2. Background Art
VoIP (Voice over Internet Protocol) is a group of technologies that are used to provide voice services using Internet protocol in packet networks. Compared with traditional circuit-switch based voice delivery technology, VoIP has a series of advantages including low cost for use and maintenance, flexibility for upgrade and expansion, facility for integration and convergency. Therefore, VoIP becomes an emergent technology in communication world and revolutionizes the telephone networks and services. Session Initiation Protocol (SIP) is the application-layer signaling protocol in VoIP for creating, modifying and terminating communication sessions. SIP's power of simplicity, flexibility and extensibility makes it more and more prevailing in communication area.
A SIP network is a group of SIP-enabled entities connected to communicate with others through communication links. In recent years, lots of SIP networks have been deployed in enterprises and communication carriers' domain to provide VoIP services. With the extension of SIP VoIP network scale, the management challenge is raised to network administrator. To manage SIP network efficiently, administrator needs to know an important aspect of the SIP network—topology, the application-layer layout of the interconnections and routing information among linked SIP entities.
Topology information is very important to network management and network layout. With topology information, the network administrator may manage the network more efficiently, improving the network capability. For example, the warning information can be showed on the topology figure intuitively when a SIP device has failure. And the network administrator can find the location where the failed device locates rapidly, predict the problems that would be brought by the network capability drop caused by the failure, and justify and set with the topology information to avoid such cases occur.
How to obtain the topology information of a network is an important issue in network management. Topology discovery is such a technology to obtain and report network topology information. A simplest topology discovery method is to request the network administrator input the location information of devices and the connecting links between them manually and draw out network topology figure directly. Although this method is simple, it would become boring and low efficient when the number of devices is large, and the quality is difficult to control. Therefore, automatic topology discovery technology is needed to complete this task. The following technologies are related to the area of automatic topology discovery.
U.S. Pat. No. 6,205,122 discloses a system and method for automatic detection of physical network topology, by correlating information from computers connected to the network. This information is gathered through the operation of a plurality of agents, which are distributed throughout the network and which are operated by a computer connected to the network. The agents exchange information in order to at least partially determine the physical topology of the network.
U.S. Pat. No. 6,697,338 discloses a method for determining physical connectivity between elements in a multiple subnet communication network. Address sets are generated for each interface of the network elements, wherein members of a given address set correspond to network elements that can be reached from the corresponding interface for which the given address set was generated. A set of candidate connections between an interface of the given network element and one or more interfaces of other network elements are determined. If more than one candidate connection is determined, connections with network elements that are in the same subnet as the given network element are eliminated from the set.
U.S. Pat. No. 6,681,248 discloses a method to track the connectivity of the network uses the trace messages. In this method, a network manager creates a list of ports in the network and uses that list to track the connectivity. For each port, the manager first checks whether there is a current connection and if it finds one, records the connection. For the unconnected ports, the manager enables the transmission of a trace message that identifies the transmitting port. When a trace detected message is received from a port, the network manager updates the list of ports with the connection just reported and disables the trace message that was detected.
However, those methods focus on physical-layer or network-layer interconnections in specific networks. And they cannot solve the difficult issues raised by SIP networks. SIP protocol is an application-layer signaling protocol. Compared with the physical-layer or network-layer protocol in the above methods, SIP network topology is different in protocol message format, entity detecting method etc. Furthermore, between the entities in SIP network there is logic connection relationship, which is different from the connection on physical-layer or network-layer. The transferring paths of SIP messages between the SIP network entities are not on the same level with physical-layer or network-layer, and could not be represented by the existing routing on physical-layer or network-layer. Therefore, the existing topology discovering methods could not be applied on SIP network. It's desirable to provide a new topology discovering method and system which can be applied on SIP network.